Polymers such as low density polyethylene homopolymers and copolymers, particularly those incorporating polar comonomers (e.g., vinyl acetate), become more difficult to pelletize as the melt index increases. Conventionally, pelletizing such polymers has required methods such as reduced production rates, optimizing extruder and pelletizer conditions, and/or cooling the polymer by various methods involving heat transfer to a cooling fluid or vapor. Because of the high viscosity of the polymers, heat transfer coefficients are low and the resulting reduction in temperature is limited and often unsatisfactory. Optimization of extruder and pelletizer conditions has a narrow range of application, especially for softer copolymers.